Thermal Expansion of Uranium and Tantalum Monocarbides up to 2700°C

Data are reported from experiments performed to measure thermal expansion of uranium carbide up to the meltin, point, the expansion accompanying the transition from solid to liquid, and thermal expansion in the liquid phase. The thermal expansion of the tantalum carbide crucibles, used to hold the uranium carbide specimens, was also measured. Experiments were performed using a high-temperature, helium-atmosphere, tungsten filament furnace. Compatibility tests showed that tungsten-graphite and tungsten-tantalum carbide pairs fused together at ∼2400°C; tantalum carbide and graphite remained compatible to 2800°C over the time scale necessary for the expansion measurements. Changes in the length of each expansion sample were measured by detecting electrical contact between the sample and a graphite rod. For measurements in which the uranium carbide was molten, a tantalum carbide disk was placed at the end of the graphite rod to prevent attack of the sensing rod by the molten uranium carbide. Melting point of the uranium carbide samples was 2550°C. The average uranium carbide linear thermal expansion from room temperature to the melting point is 17 × 10⁻¹/°C. Volume expansion upon melting of uranium carbide is 11.4%. A provisional linear thermal expansion of 35.2 × 10⁻¹/°C was measured for molten uranium carbide thermal expansion between 2650 and 2740°C.